© Copyright 2016 OGF - Polling – Fission Product Poisons Reactor Theory Fission Product Poisons

© Copyright 2016 OGF - Polling – Fission Product Poisons 1.A fission product poison can be differentiated from all other fission products in that a fission product poison will... A.be produced in direct proportion to the fission rate in the core. B.remain radioactive for thousands of years after the final reactor criticality. C.depress the power production in some core locations and cause peaking in others. D.migrate out of the fuel pellets and into the reactor coolant via pinhole defects in the clad.

© Copyright 2016 OGF - Polling – Fission Product Poisons 2.Which one of the following is a characteristic of xenon-135? A.Thermal neutron flux level affects both the production and removal of xenon-135. B.Thermal neutrons interact with xenon-135 primarily through scattering reactions. C.Xenon-135 is primarily a resonance absorber of epithermal neutrons. D.Xenon-135 is produced from the radioactive decay of barium-135.

© Copyright 2016 OGF - Polling – Fission Product Poisons 3.Immediately after a reactor trip from sustained high power operation, xenon-135 concentration in the reactor will... A.increase, due to the decay of iodine-135. B.decrease, because xenon-135 production from fission has stopped. C.remain the same, because the decay of iodine-135 and xenon-135 balance each other out. D.decrease initially, and then slowly increase due to the differences in the half-lives of iodine-135 and xenon-135.

© Copyright 2016 OGF - Polling – Fission Product Poisons 4.One hour after a reactor trip from sustained 100 percent power operation, the xenon-135 removal process consists primarily of... A.beta decay. B.gamma decay. C.neutron capture. D.gamma capture.

© Copyright 2016 OGF - Polling – Fission Product Poisons 5.Xenon-135 undergoes radioactive decay to... A.iodine-135. B.cesium-135. C.tellurium-135. D.lanthanum-135.

© Copyright 2016 OGF - Polling – Fission Product Poisons 6.Reactors A and B are operating at steady-state 100 percent power with equilibrium xenon-135. The reactors are identical except that reactor A is operating near the end of core life (EOL) and reactor B is operating near the beginning of core life (BOL). Which reactor is experiencing the most negative reactivity from equilibrium xenon-135? A.Reactor A (EOL), due to a greater equilibrium concentration of xenon-135. B.Reactor A (EOL), due to lower competition from the fuel for thermal neutrons. C.Reactor B (BOL), due to a greater thermal neutron flux in the core. D.Reactor B (BOL), due to a smaller accumulation of fission product poisons.

© Copyright 2016 OGF - Polling – Fission Product Poisons 7.A reactor has been operating at 25 percent power for 24 hours following a two-hour power reduction from steady-state 100 percent power. Which one of the following describes the current status of the xenon-135 concentration? A.At equilibrium. B.Decreasing toward an upturn. C.Decreasing toward equilibrium. D.Increasing toward a peak.

© Copyright 2016 OGF - Polling – Fission Product Poisons 8.A reactor had been operating at 100 percent power for several days when it was shut down over a two- hour period for maintenance. How will the xenon- 135 concentration change after the shutdown? A.Peak in 2 to 4 hours and then decay to near zero in about 1 day. B.Peak in 2 to 4 hours and then decay to near zero in 3 to 4 days. C.Peak in 6 to 10 hours and then decay to near zero in about 1 day. D.Peak in 6 to 10 hours and then decay to near zero in 3 to 4 days.

© Copyright 2016 OGF - Polling – Fission Product Poisons 9.A reactor was operating at 100 percent power for 2 months when a reactor trip occurred. Four hours later, the reactor is critical and stable at 10 percent power. Which one of the following operator actions is required to maintain reactor coolant temperature stable over the next 18 hours? A.Add positive reactivity during the entire period. B.Add negative reactivity during the entire period. C.Add positive reactivity at first, and then negative reactivity D.Add negative reactivity at first, and then positive reactivity

© Copyright 2016 OGF - Polling – Fission Product Poisons 10.A nuclear power plant is initially operating at steady-state 100 percent reactor power in the middle of a fuel cycle. The operators then decrease main generator load to 90 percent over a one-hour period while adding boric acid to the reactor coolant system. After the required amount of boric acid is added, reactor power is 90 percent and average reactor coolant temperature is 582°F. All control rods remain fully withdrawn and in manual control. If no other operator actions are taken, which one of the following describes the average reactor coolant temperature after an additional hour? A.Higher than 582°F and increasing slowly. B.Higher than 582°F and decreasing slowly. C.Lower than 582°F and increasing slowly. D.Lower than 582°F and decreasing slowly.